A major part of the past research on food emulsions has focused on the emulsifying processes that produce fine oil droplets and the long-term stability of resultant emulsions, and such research topics are still indispensable. Consumers' preference for more natural and healthier foods, including emulsion products, promotes the development of new emulsifying agents. However, such new types of emulsifying agents should be subjected to testing for emulsifying ability and emulsion stability before commercialization. Furthermore, the current emulsion products should withstand various stresses during the storage, transportation and consumption processes, e.g., freeze-thaw cycles, which need expansion of emulsion stability evaluation. On the other hand, new topics on emulsion research focusing on the phenomena “after ingestion” are attracting increased attention of food scientists. In particular, the attention is focused on the relationship between changes in emulsifying state and sensory evaluation in the mouth and the digestion behavior of emulsions in gastro-intestinal tract (GIT) affecting biological functions such as controlled release and absorption of target materials.
In this issue, recent trends in emulsion research covering areas from a novel emulsifying agent, a new method of emulsification, and emulsion stability to phenomena after ingestion are reported in five articles. Sato introduces information about a novel emulsifying agent, gum ghatti from Anogeissus latifolia, emphasizing the superiority in emulsifying activity and emulsion stabiity over gum arabic which is widely used for emulsion products. Ishii et al. describes the application of fine particles as a new emulsifying technique by showing their recent results on emulsions produced via the Pickering and Mickering stabilization mechanism. The application of natural lipid assembly, soybean oil body as an emulsifying agent, is also included in this article. The other three articles are related to the events after ingestion of emulsions. The article of Liu et al. provides an overview of fundamental knowledge, recent findings, and the relation to health promotion with respect to the digestion processes of foods with complex structures including emulsions in the gastrointestinal tract (GIT). The most important viewpoint emphasized by Liu et al. is that the destructuring and restructuring of foods within the GIT plays a key role in the digestion and absorption of food components, including both nutrients and non-nutrients having bioactive functions and subsequent physiological responses. Matsumiya et al. discusses the effects of structural and physical properties of emulsions before ingestion, e.g. , oil droplet size and distribution and rheological and tribological properties on the palatability evaluation after ingestion. In addition, they pointed out the importance of paying attention to the aspect of how food destructuring of emulsions occurring in the mouth affects palatability by referring to the contribution of dynamic change in flavor release behavior. Nakagawa introduces his recent challenge to design lipid-based nanoparticles for targeted delivery of active ingredients to various regions in GIT. He employs a technique to prepare multi-phase lipid particles to attain the controlled release of embedded materials triggered by lipase.

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Foods are complex structures containing assemblies of macronutrients and micronutrients. Food structures and matrices are modified in the gastrointestinal tract, involving complex biochemical and physical processes. Recent knowledge on the restructuring of food within the gastrointestinal tract has extended the understanding of the role of the food matrix in the digestion and absorption of nutrients and the subsequent physiological responses. By characterizing the structuring of food within the gastrointestinal tract and the impact of the food matrix and the interactions between food nutrients on their bioavailability, innovative foods could be created with specific impact on human health. This article provides an overview of food structures, digestion processes and aspects of how food structures and food components are digested and absorbed in the gastrointestinal tract.

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Many foods including creams, sauces, and dressings exist as an oil-in-water (O/W) emulsion, where small oil droplets are dispersed in a continuous aqueous phase. Food emulsions are usually manufactured by homogenizing immiscible oil and water phases with amphiphilic molecules such as small-molecule-surfactants and proteins as emulsifying agents, which can adsorb on the newly-created oil droplet surfaces to form protective layers on the droplet surfaces. Because O/W emulsions consist of two immiscible phases and thus are thermodynamically unstable, O/ W emulsions inevitably undergo undesirable physical phenomena such as creaming, flocculation, and coalescence to ultimately separate into bulk oil and water phases. Therefore, the kinetic stability of emulsions against these physical phenomena until consumption is critically important for maintaining quality of emulsified food products. While most fundamental research on food emulsions has been carried out using the nano-ordered amphiphilic molecules, trends in food emulsions are shifting toward meso- and micro-scale particles as a novel class of emulsifying agents during the last decade. In this review, recent studies on particle-stabilized emulsions are overviewed, and our work on emulsifying properties of various colloidal particles are reviewed. Our findings indicate that powders derived from agricultural products (e.g., rice grain, mushroom, plum fruits, and avocado fruits), microgels fabricated from polysaccharides(i.e., micron-sized polysaccharide gel particles), and lipid-protein complex particles (i.e., natural soybean oil bodies) can act as emulsifying agents in various model emulsified food systems. The research progress in particle-based emulsion systems will potentially lead to developments of novel emulsifying agents, which can meet diversifying consumers demands for daily food products and social requirements towards Sustainable Development Goals (SDGs).

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Many food products either partly or wholly exist as an emulsion where a liquid disperses as small droplets in another immiscible one. Food emulsions are usually composed of oil and water in the food industry and include milk, cream, mayonnaise, and coffee whitener. The palatability of food emulsions that mainly involve preferred taste, texture, and flavor is dependent on the materials formulated but also on the nature, structural and physical properties of the manufactured emulsions. In this article, effects of the properties at the initial state on the palatability of oil-in-water type emulsions are discussed, followed by arguments on the impact of dynamic changes in the mouth, a recent trend of food research. While the variety and content of oils and fats and small molecule emulsifiers often modified the mouthfeels of the emulsions, the oils and fats content predominantly affects the released aroma. An increased viscosity with added thickening agents significantly enhances creaminess of the emulsions among oils and fats-related sensations. During the mastication of the emulsion, they dynamically change in their physical states to be more thermodynamically stable via creaming, flocculation, and coalescence. The significance of qualitative and quantitative changes of the orally processed emulsions was systematically analyzed for relating to perceived creaminess, fattiness, and thickness. On the other hand, effects of the changed physical states on the aroma profile are still controversial. Further research will be required for aroma components, orally processing conditions, and so on. The authors emphasized that the dynamic changes in consumption ought to be linked to fortified palatability of the food emulsions for the benefit of the consumer.

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Lipid-based particulate systems are increasingly being recognized as potential delivery vehicles for nutraceutical materials. Nanostructured lipid carriers (NLCs) are lipid-based systems that contain nanometer scale structures built by lipid blends. Numerous NLCs that develop preparation methods and illuminate the relationship between structural features (i.e. particle geometry, encapsulation efficiency, phase transition property, etc.) and biological functionalities have been proposed in recent studies. It is an important challenge to design particles for targeted delivery of active ingredients to various regions in the gastrointestinal tract. It is thus desirable to develop a practical technique to manufacture NLCs that enables characteristic designs using biocompatible excipients. This article presents a technique to prepare multi-phase lipid particles by using a mixture of carnauba wax and coconut oil. A high shear homogenization method was employed for the particle preparation. It is expected, through this processing, that the nanostructured oil phases are embedded in the main body of the waxy particle. When these particles are subjected to digestive solution, the oil phases are digested releasing free fatty acids and entrapped materials in the oil phase. This article presents how this conceptual design was demonstrated for triggered release by lipase. Water droplets containing ferric ion were emulsified in coconut oil and this water-oil emulsion was used in the preparation of multi-phase lipid particles. The multiphase lipid particles with a mean size of around 9 μm were successfully prepared and the ferric ion was released by the action of lipase.

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Gum ghatti is a natural polysaccharide obtained from Anogeissus latifolia. Gum ghatti possesses emulsifying properties that are superior to those of gum arabic. Main components of gum ghatti include carbohydrate and protein, ash, water, and a small amount of tannin. The main structure of gum ghatti is a highly branched arabinogalactan, and a highly hydrophobic protein adheres at its oil droplet surface. These carbohydrate chains and protein provide the emulsifying properties of gum ghatti. The standard of gum ghatti was revised in the 89th Joint FAO/WHO Expert Committee on Food Additives (JECFA) meeting held in 2017, and L-rhamnose was added to the gum constituents. At present, gum ghatti consists of L-arabinose, D-galactose, D-glucuronic acid, D-mannose, D-xylose, and L-rhamnose. Furthermore, in the 89th JECFA meeting, safety evaluation of gum ghatti was performed and an ADI was established as "not specified". After that, gum ghatti was listed in General Standard for Food Additives (GSFA) Table 3 in 2019. The excellent emulsifying ability of gum ghatti is applied to a variety of processed foods, and gum ghatti can stabilize oil/water emulsions.

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Women today have a very long life after menopause. The lack of estrogen due to the cessation of ovarian function increases various health risks for women. Hormone replacement therapy is applied to treat menopausal symptoms. However, research on alternative therapies for menopausal symptoms accelerated after large-scale clinical trials found that estrogen increased the risk of breast cancer and thrombophilia. Among polyphenols, phytoestrogens, which exhibit estrogen-like effects, have attracted much attention. In particular, many randomized control trials have been conducted using soy isoflavones, but the efficacy of isoflavones is not yet certain. Recently, it was found that equol, a metabolite of soy isoflavone produced by intestinal bacteria, is the key to its effectiveness. The effectiveness of other phytoestrogens, such as black cohosh, maca, and pueraria, in alleviating menopausal symptoms is inconclusive due to the lack of standardization of ingredients and quality. On the other hand, osteoporosis in postmenopausal women is a factor in becoming bedridden or requiring nursing care, and significantly reduces the quality of life of elderly women. Polyphenols have received much attention for the treatment and prevention of osteoporosis. Some polyphenols, such as phytoestrogens, improve bone metabolism by binding to estrogen receptors in bone, while others, such as tea catechins and olive oil polyphenols, reduce the risk of fractures during menopause by reducing DNA damage caused by reactive oxygen species. Based on the results of studies to date, it is still difficult to show a clear health benefit of these polyphenols. Since many polyphenols exist as complexes, it is important to investigate the effects of combinations. In addition, the metabolism of polyphenols by intestinal bacteria and subsequent absorption in the gastrointestinal tract remains unclear. In the future, it will be necessary to conduct more large-scale, long-term clinical trials to accumulate evidence on the role of polyphenols in women's health.

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In recent years, use of genetic recombination technology for introducing foreign genes into living organisms has been developed, and genetically modified soybeans and corn strains with traits such as herbicide and pest resistance have been widely cultivated all over the world. Strict safety assessments and management of genetically modified crops are carried out by the governments of each country. In the 21st century, genome editing technology based on the ability to cleave a specific site of chromosomal DNA has been put to practical use, and many genome edited crops and livestock have been developed. Therefore, in Japan, the Ministry of Health, Labor and Welfare (MHLW) has established regulations regarding handling of foods to which genome editing technology is applied. Genome-edited foods contain no foreign genes and are obtained by modifying or destroying native genes. Therefore, it is considered to have the same level of safety as crops produced by conventional breeding methods. Developers of genome-edited foods are required to notify the MHLW, and the MHLW will confirm the outline of genome editing and the absence of foreign genes through prior consultation. In December 2020, the first application for high gamma aminobutyric acid (GABA)-containing tomatoes produced by genome editing was accepted by MHLW, paving the way for distribution and sales.

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This is a report dealing with criteria for judging the taste of beef. The taste of Wagyu beef in Japan is described from various points of view. Words such as "WAGYU", "KOBEbeef" and "A5" are often used to describe the taste of Wagyu beef. However, what are the actual factors that support those words? A well-known indicator of the distribution value standard for Wagyu beef is the grade. The grade is simply decided by yield and fat crossings. These indicators can be used to determine a distribution value, but they are not actual indicators of good taste. On the other hand, there are physical and chemical analysis values. Wagyu has umami, a fatty acid aroma called wagyu aroma, as well as melt-in-your-mouth tenderness, and so on, representing its characteristics. It is possible to measure these characteristics numerically and visualize them, but can we use those values as the basis for describing the taste of the food? I believe that these existential factors do not explain the taste of Wagyu, but psychological function does. I think it is necessary to assume that taste has diversity before it is measured by characteristic values.

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An (bean jam) is an indispensable foodstuff used in Japanese cake, and was introduced from China in the seventh century. However, Chinese An (a food used for stuffing) was a foodstuff which utilized meat and other materials with medicinal functions. Japanese An utilized azduki bean instead of meat because meat was forbidden in ancient Japan. The manufacture process of An was established using many different methods in the Edo era (1603~1868). At present An is made from azduki bean and other pulses, except soybean and peanuts, by soaking in water, cooking, grinding, removing hulls, washing, adding sugar and kneading. An is the traditional foodstuff that best captures the characteristics of the beans perfectly.

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